1. Field of the Invention
This invention relates to a puffer type gas-blast circuit breaker, wherein an arc extinguishing gas is compressed by a piston and cylinder device during a trip action.
2. Description of the Prior Art
With the recent trend to higher voltages and greater capacity in power transmission systems, the short-circuit currents that must be interrupted by circuit breakers have suddenly increased, and the voltages which are applied to circuit breakers after current interruption have also continuously tended to increase. To improve circuit breaker performance it is therefore absolutely essential to raise the dielectric strength between the electrodes.
As disclosed in U.S. Pat. No. 3,728,504, the puffer type gas-blast circuit breaker of the prior art includes an arc extinguishing chamber which consists of a movable electrode which is fixed only to a grounded tank and a fixed electrode which is supported relative to the movable electrode by a rod type capacitor to distribute uniformly the voltage over the electrodes during the current interruption.
As disclosed in another embodiment of the prior art, a puffer type gas-blast circuit breaker includes an arc extinguishing chamber covered by a cylindrical capacitor for improving the voltage distribution over the electrode during current interruption in order to prevent the compressed arc extinguishing gas flow directly into the grounded tank from the arc extinguishing chamber.
Thus when the high-temperature gas, through which passes the arc which is generated during circuit breaking, is blown out from the gap formed between the extreme end of the fixed side of the conventional grounded tank puffer gas-blast circuit breaker and the extreme end of its insulating nozzle, in the open condition, into the inside of the surrounding insulating tube or cylindrical capacitor, heat penetrates into the inside surface of the insulating tube or cylindrical capacitor, causing deterioration, and in particular carbonization. This lowers the degree of insulation provided by the inside face of the insulating tube or cylindrical capacitor. As a result its performance cannot be improved.